Crystal detector



. F. J. MARTIN CRYSTAL DETECTOR Filed Jan. 21, 1925l o Zo /5 :n:

WW f' JNVENTOR. /71-40 d. MART/N Patented May 22., 1928.

'ETES ATENT- FFICE FRED J. MARTIN, OF OAKLAND, CALIFORNIA.

CRYSTAL DETECTOR.

Application led January This invention relates broadly to radio apparatus and specifically to detectors of the crystal type.

I have found from practice that contact b etween the selected sensitive spot of a crystal and its coacting electrode, commonly called cats Whisker, can be definitely maintained or preserved against the action of extraneous vibrations by yieldingly holding the electrode or cats whisker against lateral movement at a point to one side of the crystal. i By this newly discovered means, no interruption is caused in a radio circuit through temporary dislocation of the electrode from itsA crystal as was the case in this type of instrument as heretofore devised and known. j

My invention is characterized by a crystal holder and means for associating` an electrode with respect to the crystal so as to hold the former and the latter against relative movements when a selected spot on the crystal is found.

More specifically, my invention is characterized by a crystal holder which can be moved universally with respect to its coacting electrode so that a very large rangeof selectivity can be had, and means for holding the electrode against shifting in a lateral direction after desired adjustment thereof has been obtained. y j

l/Vith the above and otherobjects in view which will appear as the nature of the invention isbetter understood, the same consists in the improved construction and novel arrangements of parts which will hereinafter be fully described and particularly pointed out in the claims.

In the accompanyingdrawings has been illustrated a single and preferred form of the invention, it being, however, understood that no limitations are necessarily made to the precise structural details therein exhibited, but that changes, alterations and modifications within the scope of the claims may be resorted to when desired.

Figure 1 is a vertical longitudinal sect-ion through the detector 5 Figure 2 is a section taken on line II-II of Figure 1;

Figure 3 is an end View of the yieldable body; and

Figure 4: is a section on line IVIV of Figure l.

In carrying the invention into practice, use is preferably madekof a barrel 5 which trode, which I will describe presently.

21, 1925. Serial N0.'73,854.

may be formed of insulating material. At one end the barrely is formed with a head 6 havinga relativelylarge central opening 7. The opposite end of the barrel is exteriorly threaded at y8 to accommodate the correspondingly internally threadedtiange 9 of a cap 10. This cap is formed of met-al,I and sameis provided with an integral extension 11 having a central threaded bore 12, and an external thread 13, the free end of the extension being split radially at 111 so that portions of the extension can bev adjusted with exposed as shown in order that it may be brought into active contact with the elec- This crystal holder lcarries ka screw 18 which ex-v tends through the large opening 7y so that it may be moved `laterally and in fact universally with respect to the walls of said opening. In this manner, the position ofthe holder 16 may be changed with respect to Inthis respect I do not wish to the center ofthe barrel. Any desired adjustment of the crystal holder can be obtained by means of the clampnuts 19 and 2O which .are mounted on the screw 18. This screw acts in the capacity of a binding postand connected with the screw and with the nuts 19 and 20 is a metal clip or plate 21 which may be arranged in an electric circuit. l

'Within the barrel at a point between the crystal 17 and the head 1() is a cylindrical elastic'or yieldable body 22, preferably, but not necessarily, formed of cork, the latter being found very desirable for the purpose intended. The external diameter of the body 22 is substantially co-extensive with the internaldiameter of the barrel 5 to the extent that the body 22, may be moved axially of the barrel and against or toward the crystal. y i

A follower plate 23 is mounted behind the body 22 at one side of the cap 10 so asv to be advanced against the body on the application of pressure to the plate. Movable in the bore 12 of the extension 11 is a feed screw 24 having its free end formed with a nurled manipulating knob 25. The opposite end df the screw has a reduced threaded portion 2G extended into a correspondingly threaded aperture in the follower plate 23. Said extension 26 carries an electrode 27 which in the present instance consists Vof a single length of wire normally about co-eX tensive, or less in length/than the `body 22. y The. extension l2 of the cap l0 forms a binding po'stforthe secondl terminal of the circuit in which the crystal is mounted,.and in view thereof the ,extension is provided With clamping nuts28 and 29 between which a 'wire receiving' clip 30 is clamped. The extension also carries a clamping nut 3l which embraces t-he split portions of the extension 'l2 so that same can be advanced into locking contact with the screw 24 to hold the latter in a relatively fixed position vof loli'gitudinal adjustment.

Having described the details of construe tion of my vimproved crystal detector, their operation is advanced as follows:

A desired position ofthe crystal is first obtained Within the barrel and the electrode 27 is brought into vitsy vselected position With the spot desired. As previously stated, the electrode or cats Whiskerl is substantially co-extensive with, or less in length than, the body 22, and consequent-ly it does not protrude therefrom. When `the follower plate 23 is advanced toward the head' under the action of the screw 2l, the body 22 is gradually advanced toward thecrystal. As this f body tends to compress, it follows that the effective contact end of the electrode or cats Whisker, being normally shorter `than the body 22, naturally tends to protrude from the adjacent facejof the body at the crystal so that it finds active circuit contact with the selected spot on the crystal. Also at this time the annular surface of the body 22 is hugged 4or snugly embraced 'by the lWalls of the barrel 5,

`Incident thereto, the electrode or c ats Whisker 27 is guarded against accidental displacement from the crystal through the act-ion of extraneous vibrations. Inr crystal detectors of the type heretofore known the electrode or cats Whisker is extremely 'deli- `cate, and one shaking the same accidentally or through the act of Walking over a floor or jarring the radio instrument would. cause dislocation of the electrode with respect to the crystal, and immediately the instrument is thrown out of circuitand it 'becomes necessary for the operator to select 'another vsensitive spot in order that theset will properly function. jeetion, and by the means employed herein secure a position yof relative permanency of the electrode or catls Whisker With respect to t'heselected spot on the crystal; and once an adjustment is had or a selected spot found, ordinary vibration will not in any way affect the: Circuit of the set. Y

. As previously stated', il am broadly 'interested in vthe provision ofmeans capable of being associated with the electrode or 'cajts Whisker ofa crystal detector1 so aste hold same against vibration laterally and maintain its position in effective vcontact with its coacting crystal. In vie-w thereof,"l donot wish to be limited to the precise detail-s of constructienk herein employedv nor to the fn-a- I am able to eliminate this obterials used. vI refer to` A`cork'afsloeing'very desirable when constructing a body 22' that Will yield Vvand function satisfactorily 'als herein set forth. Any well-known composition of matter which will 4'enable the/electrode or cats Whisker to be protrud'ed'ffrom a surface thereof and Aopei'vati'vely positioned With respect to the crystal Will or might suiiice for my purpose.

Lateral displacement of 4the elect-rode is guarded against the means herein `set forth and just described. Longitudinal displacement vis guarded against by means 'of the nut 3l functioning through the lsplit portions of the extension 12 to bindsaid portions and temporarily lock same againstv the threads of' the screw 24. These nioeties of construction permit the crystal to function in a highly satisfactory manner.

I claim:

l. A crystal detector comprising a barrel containing a crystal, an elastic body in the barrely movable Wit-h relation to the crystal, and a cats Whisker penetrating the'body so that its tip ymay be exposed therefrom and presented to the crystal, the said body be* ing snugly embraced by the Walls fof the barrel.

2. A crystal detector comprising -a bar-rel containing a crystal, an :elastic'body in the barrel movable with relation toy the crystal, and a cats Whisker penetrating-'the fbody so that vits tip may be exposed therefrom and presented Ato the crystal, the said body lbei-ng snugly embraced by the walls o f the barrel, and means for holding the cats Whisker against longitudinal movement.

FRED J. MARTIN. 

